There was a point during the early days of The Big Bang Theory where it was hard to imagine a day when Sheldon Cooper (Jim Parsons) would stand closer than 5 feet to another human being. But who knew a day would come when we’d actually be having a conversation about Sheldon’s first kiss?

After last week’s episode, that’s exactly where we find ourselves – marveling at the progression of an odd creature character once thought to be set in his ways. Not to say he still isn’t, however. In fact, if there’s one amazing thing about the incredible lip-lock Sheldon shared with Amy (Mayim Bialik), it’s that, according to executive producer Steve Molaro, the writers found a way to both honor the character’s beloved uniqueness and inch him forward. In the conversation below, Moloro elaborates on that point and tells EW how the moment came together.

ENTERTAINMENT WEEKLY: Tell me about the conversations you had in the writers’ room leading up to this episode.STEVE MOLARO: We knew we were going to do this Valentine’s Day episode where Amy manages to get Sheldon to go up to Napa for the weekend by using the train as bait. And you know, their relationship is great, but I think there’s only so much Amy can take. We do need to keep it moving forward even if it’s in baby steps, and I was just feeling that it was time. She deserved a big win, and this seemed like a good way to get to it. Rather than it coming from his excitement, [we wanted] it to almost stem from an argument. It seemed like an exciting way for it to happen.

Was there ever a discussion about possibly having it stem from a moment where he was happy or wanted to kiss her sans argument?
There were many discussions, yes. But this sort of was the way we initially had seen it, and then we tinkered with it a lot and talked about it a lot and ultimately it was pretty close to the original idea. So that was overall nice to see. I guess what I can tell you is that we liked it stemming out of an argument, but there was sensitivity to making sure that Sheldon was never actually too mean during it. Jim was so masterful at playing it right on that line that I think it was a beautiful thing to watch

Tell me about filming it.
I can tell you the script – the way the kiss was described in the script – it said, “Sheldon leans in and puts his lips on hers and after a few moments, it melts into a real kiss, the kind of kiss that mommies and daddies do.” That was the action line, because it was referring to a joke that Sheldon had said about kissing when Amy was daydreaming about them kissing. No one watching at home will ever know that, but at our table read, our director Mark [Cendrowski] got to say that out loud as he was describing the kiss. I thought it was a really good way to describe what we were hoping to capture, and I think it was – it was one of those kisses that mommies and daddies do.

Tease for me what comes next.
That’s an important question. We’re not going to do too much relationship stuff between Sheldon and Amy right away, but obviously this is a moment that occurred and you’ll hear about it here and there. But sometimes we like to make a big move and then put that aspect down for a few episodes before we revisit it. But it happened. He clearly didn’t dislike it. It turned out to be not as bad as he thought it would be – as he described to Leonard when he got home. And we’ll see where they go from there. I imagine she would want more than that or she’ll try to work that into the way hand-holding has sort of become a regular thing. Maybe date nights will end with some sort of kiss. I don’t know, to be determined.

Leonard’s reaction was fantastic.
That scene was actually a bit of a last-minute addition. I mean, that kiss was such a beautiful moment. And you could have easily ended the episode on it. But we felt it would be nice to see that there was no giant shift in who Sheldon was. That, while there was a small shift and he didn’t dislike the kiss, he’s still Sheldon. I thought that was a way for that scene to show that. So there was a little growth – he didn’t dislike the kiss, but he also liked when the conductor played the banjo and meeting his new friend, Eric, who loves trains as much as he does. They were all great. In his mind, one was no better than the other. They’re just events that occurred that night, which I think was still a fairly Sheldon-y way of looking at it.

Are we going to see Eric again?
There are no immediate plans. But that actor did an incredible job and he was really fun to have around and Sheldon and Eric are undeniably friends, and I think as long as there is a train system, he can be near Pasadena whenever he would like. So no immediate plans, but if we can come up with a fun story that would include him, I would love that.

Did Jim and Mayim say anything to you after they read the script for the first time, or do you know what their reaction was?
I don’t know, per se. But they take these moments incredibly seriously and they work very hard. And after the first run-through, the stage was just silent. The first rehearsal where we saw them actually do it, it was just chilling. I emailed them later that night just to say, “That was just so truly amazing.” They were feeling really good about it, and they were happy to hear that the rest of us on the stage also felt that way.

Note: CBS also released a video of Jim Parsons talking about the clip. Here’s that video: